COVID-19 cases are on the rise among young adults, but health experts aren’t sure why

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People in their 20s are helping to drive transmission of COVID-19 in many Ontario hot spots, but public-health experts say it’s unclear where they are getting infected, which could hamper efforts to contain further spread.

The issue is taking on increasing urgency as the Greater Toronto Area, Hamilton, Windsor and other populous parts of the province cannot move to the next stage of reopening their economies until they reduce their numbers of new cases.

For example, Toronto still has an average of 140 new cases a day.

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In recent weeks, the number of people in their 20s testing positive for COVID-19 in areas such as Toronto and Hamilton has risen compared with older age groups.

In Hamilton as of June 8, people in their 20s accounted for 40 per cent of all new COVID-19 cases reported in the previous 10 days. Over the same time period, people in their 50s accounted for 17.5 per cent of cases, while people in their 70s accounted for 5 per cent of cases. City officials are planning a social-media campaign to target young people about the risks of COVID-19.

Elizabeth Richardson, Hamilton’s Medical Officer of Health, said the upswing in cases in young people doesn’t appear linked to any particular workplace. Officials believe some people became infected during activities such as commuting, she said.

According to figures from Public Health Ontario, people in their 20s accounted for 31.5 per cent of new COVID-19 cases across the province on June 7, compared with just 12.6 per cent on April 26.

“Clearly, there were people in their 20s who were clustering together who were facilitating transmission of this infection,” said Isaac Bogoch, an infectious diseases physician at Toronto General Hospital.

Lauren Lapointe-Shaw, a general internist and clinical epidemiologist at Toronto’s University Health Network, said young people likely made up a substantial number of Ontario’s COVID-19 cases all along. But because the province had strict criteria on who could get tested until very recently, such as those with severe symptoms, many of the cases involving people in their 20s – who are more likely to have a mild illness – may have gone undetected, she said.

“Not diagnosing these people meant they were potentially infecting others,” Dr. Lapointe-Shaw said. “They didn’t have the chance to know they were infecting others.”

A huge public outcry erupted last month after thousands of people, most of them young, congregated in Toronto’s Trinity Bellwoods Park, many of them shoulder-to-shoulder. Earlier this week, Toronto’s Medical Officer of Health, Eileen de Villa, said there has been no spike in COVID-19 cases related to that day.

But Gerald Evans, chair of the division of infectious diseases at Queen’s University in Kingston, said it’s possible many were infected that day and didn’t get tested.

Barbara Yaffe, the province’s Associate Chief Medical Officer of Health, in a briefing earlier this week also suggested that increased testing among the younger cohort may be playing a role.

“I would think part of it is that we’ve opened up testing to people with less severe symptoms, in fact, with no symptoms,” she said. “I don’t think we have a breakdown at this point of exposure sites by age group. So, it’s hard to say.”

Experts say that, to reduce transmission, the province needs to do a better job at figuring out how people are getting infected in the community.

Dr. Lapointe-Shaw said several of her patients with COVID-19 have no idea how they got it, and that the few trips they’ve made out of the house are to the grocery store.

According to Ontario’s data, travel accounts for about 5 per cent of COVID-19 cases in the province, while close contact with a confirmed case and outbreaks account for 62.5 per cent of cases.

But 21.5 per cent of COVID-19 cases in the province are the result of community transmission, meaning those infected don’t know where they got the virus. And 11 per cent of cases have no information about how the individuals became infected.

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